Control laws (CLAWs) may be used to enhance and improve ride quality of an aircraft when components (e.g., wings, horizontal stabilizers, etc.) of the aircraft are exposed to unsteady external forces (e.g., wind or turbulence). One or more sensors may be coupled to the components of the aircraft to detect the presence of these external forces. Under certain system failure conditions, the sensors may generate an erroneous oscillatory signal that is provided to a flight control computer of the aircraft. The flight control computer processes the oscillatory signal based on one or more CLAWs to generate commands that control operations of the aircraft. Processing the oscillatory signals based on the one or more CLAWs includes amplifying the oscillatory signal. The commands generated by the flight control computer may be used to modify or augment commands generated by pilot operated controls.
For example, an aircraft may experience a random lift variation (e.g., an increase in altitude) due to upward forces (e.g., lifting forces) when surfaces of the components of the aircraft are exposed to vertical gust. The lifting forces may be detected by the sensors which feed back to the flight control computer. Based on the signal received from the sensors, the flight control computer may command control surfaces to counteract the detected lifting forces, resulting in a smoother and more comfortable ride for the passengers on board the aircraft. However, the erroneous oscillatory sensor signals may lead to a sustained control surfaces oscillation which may cause aircraft structure fatigue damage.
Sustained oscillatory commands generated by a flight control computer may increase dynamic loads on the components of an aircraft. The aircraft components may be designed to withstand a particular dynamic load threshold (e.g., a surface load allowable) for a period of time. The flight control computer may monitor the sensor input signals to detect oscillatory failures. Oscillatory failures indicate that the components of the aircraft have experienced dynamic loads at or above the dynamic load thresholds for the period of time. When an oscillatory failure is detected, the flight control computer may deactivate the affected CLAWs, removing the induced dynamic loads on the components of the aircraft.
A nuisance trip occur when the oscillatory failure monitor is unable to distinguish the oscillatory failure signals from the normal signal variations that account for all dynamic loads experienced by the components of the aircraft in real-time. As such, because an oscillatory failure monitor does not account for the dynamic loads caused by the commands generated using certain CLAWs due to the nuisance trip concerns, there may be a aircraft system failure condition that may cause the dynamic loads experienced by the components of the aircraft to exceed the dynamic load threshold for longer than the duration of the period of time, leading to a true aircraft structure failure.